As noted in a couple of earlier comments, one of the biggest hurdles for any kind of propulsion system that directly uses antimatter will be dealing with the gamma ray emissions generated by the annihilation. Setting aside the complexity of using the gamma rays for propulsion (which may not be practically possible), I’m curious if anyone has computed the amount of shielding that would be required to protect the rest of the spacecraft from the gamma rays. Presumably any scientific payload would be completely fried by direct exposure. Do you have any preliminary calculations on the amount of shielding that would be required to protect the payload, and how much mass that might add to the spacecraft? Also of concern is the effect of high levels of gamma ray emissions on the propulsion system itself, but I assume that will be addressed in one of the future articles you mentioned.

Stephen
23 April

It’s an interesting point, but don’t forget that we opened the Pandora’s box in the 1940s with nuclear weapons and since then have lived with the possibility of destruction on a global scale. I don’t see there being any difference with antimatter.

Also, as a matter of fact Kim Jong Il already has nuclear capabilities.

With any new technology comes responsibility and I don’t believe it’s productive to approach these with the mindset of “Catastrophe A,B or C could happen, therefore we should not pursue the technology”, but more with the mindset of “Because A,B or C is a possibility we should take precautions D,E and F to do our best that they do not.”

Also, EM radiation (gamma rays) won’t be effected by any particular magnetic moment so unfortunately I don’t think that would work.

That would be for the case of positron-electron annihiliation. The by-products of proton-antiproton are neutral and charged pions which could be directed for thrust. The process won’t be anywhere near 100% efficient, but it will be a lot better than fusion in terms of total energy liberated per unit mass of propellant.

Could you use the Larmor precession (like is used in MRI’s) to align the spin so you could focus the Gamma Radiation? BTW, is the Larmor frequency the same for Antimatter as it is for Matter?

One problem antimatter has is the energy & intensity of the gamma-rays produced and then getting them going in the right direction to provide net thrust. Inefficient use of the gamma-rays means a much lower fraction of the energy liberated can be used for a rocket. Any thoughts on getting it going the right way?